Connector header grommet for an implantable medical device

ABSTRACT

Improvements in connector headers of implantable medical devices (IMDs) for making electrical and mechanical connections with a connector element of a proximal connector assembly of an electrical medical lead and components thereof are disclosed. A connector block disposed within a header body of the connector header has a threaded bore aligned with a header grommet aperture and a connector block bore aligned with a header connector bore. A penetrable grommet is disposed within the header grommet aperture, and a setscrew is threaded into the threaded bore having a setscrew socket disposed to be engaged by the tool inserted through the penetrable grommet within the header grommet aperture to enable rotation of the setscrew within the threaded bore to tighten the setscrew against or to loosen the setscrew from a lead connector element received in the header connector bore.

REFERENCE TO RELATED APPLICATIONS

Reference is hereby made to U.S. patent application Ser. No. 10/199,601filed Jul. 19, 2002, which is a continuation in part of U.S. patentapplication Ser. No. 09/767,796 filed Jan. 23, 2000, which is acontinuation of U.S. patent application Ser. No. 09/417,157 filed Oct.12, 1999 now abandoned, which is a continuation of U.S. patentapplication Ser. No. 09/159,119 filed Sep. 28, 1998, which is adivisional of U.S. patent application Ser. No. 08/904,636 filed Aug. 1,1997, now abandoned all of which are herein incorporated by reference.

Reference is also made to commonly assigned U.S. patent application Ser.No. (P-11597) filed on even date herewith for CONNECTOR HEADER SETSCREWFOR AN IMPLANTABLE MEDICAL DEVICE in the names of Jennifer J. Zhao etal., and commonly assigned U.S. patent application Ser. No. (P-7670.07)filed on even date herewith for CONNECTOR HEADER FOR AN IMPLANTABLEMEDICAL DEVICE in the names of Kevin K. Tidemand et al.

FIELD OF THE INVENTION

The present invention pertains to connector headers of implantablemedical devices (IMDs) for making electrical and mechanical connectionswith at least one connector element of an electrical medical lead.

BACKGROUND OF THE INVENTION

At present, a wide variety of IMDs are commercially released or proposedfor clinical implantation in the human body. Certain IMDs aremanufactured as discrete units that are intended to be selected by animplanting physician for a particular clinical use to be coupledtogether at implantation and to function as a unit. Typically, such IMDscomprise an implantable pulse generator (IPG) or a physiologic monitorand at least one elongated electrical medical lead that are electricallyand mechanically connected together upon implantation. Such IMDs includefor example implantable cardiac pacemakers for pacing one or more heartchamber, implantable cardioverter/defibrillators (ICDs) providingautomatic cardioversion/defibrillation, anti-tachycardia pacing andbradycardia pacing functions of one or more heart chamber,cardiomyostimulators, cochlear implants, muscle and nerve stimulators,e.g., sacral nerve stimulators, spinal nerve stimulators and deep brainstimulators, and cardiac and other physiologic monitors.

The IPGs of cardiac pacemakers, ICDs, and the various tissue, organ andnerve stimulators typically comprise signal processing and/or pulsegenerating circuitry powered by a battery and enclosed within ahermetically sealed enclosure or housing, sometimes referred to as a“can”, and a connector header attached to the housing that enablesattachment of at least one elongated electrical medical lead. Certainimplantable hemodynamic monitors also comprise a hermetically sealedhousing and connector header that enables attachment of at least oneelongated electrical medical lead. Other implantable monitors comprise ahermetically sealed housing and a sensor header that only supports asensor, e.g., an EGM sense electrode.

The hermetically sealed housings are typically formed of a conductivebiocompatible metal, although proposals have been made to formhermetically sealed housings of a non-conductive, biocompatiblepolymeric or ceramic. The opposed major sides of the IPG or monitorhousing can be shaped having substantially circular, oval or rectilinearoutlines and can have relatively straight and curved side edge sections.The opposed major sides are typically planar and disposed substantiallyin parallel, although the major sides may be bowed, convex or concave orotherwise contoured to some degree to conform to a particularimplantation site. The opposed major sides are typically supported andjoined together at their side edges by a mutual housing sidewallextending between them and having a sidewall width substantiallydefining the thickness of the hermetically sealed housing. The mutualsidewall extends through a number of sidewall turns or corners dependingon the circular, oval or rectilinear outline or combination of suchoutlines of the opposed major sides. Generally speaking, such IPG andmonitor housings are referred to as “prismatic”.

The connector header for making a connection with a proximal connectorassembly of an elongated electrical medical lead is physically attachedto a header mounting section of the common sidewall that is typically,although no necessarily, planar. The connector header typicallycomprises a header body that is fabricated of a relatively hard,dielectric, non-conductive polymer encasing and isolating electricallyconductive components from the patient's body. The connector header hasa header thickness generally corresponding to the housing thickness anda header mounting surface that conforms to and is mechanically affixedagainst a mating housing sidewall mounting surface. The connector headerhas a header height measured in a direction extending away from thehousing sidewall mounting surface and a header width measured in adirection extending along the housing header mounting surface in thewidth dimension of the housing. Various examples of connector headersand hermetically sealed housings are found in the patents referencedherein.

It is generally desirable that the connection of an electrical medicallead with an IPG or monitor be made rapidly and in a fail-safe mannerduring the initial implantation. Moreover, it is desirable to be able toexplant the IPG or monitor at a later time in order to disconnect theelectrical medical lead and either replace the IPG or monitor or replacethe electrical medical lead.

Typical IPG and monitor connector headers are formed having at least oneelectrically conductive, header connector element or connector blockembedded in the insulating material. Each connector block is connectedby means of an insulated feed-through mounted to the hermetically sealedhousing to the circuitry within the housing. Typical connector blocksare formed having a threaded bore for receiving a setscrew and aconnector block bore extending at substantially right angles to thethreaded bore for receiving a lead connector element. The connectorblock bore is axially aligned with a header connector bore extendingfrom the connector block through the header body to an exterior surfacethereof. The threaded bore and setscrew are axially aligned with afurther header aperture extending from the connector block through theheader body to an exterior surface thereof.

At implantation, the proximal connector assembly of the electricalmedical lead is inserted into the header connector bore to locate a leadconnector element, e.g., a lead connector pin or ring, within aconnector block bore. A tightening tool, e.g., a hex wrench, is insertedthrough the further header aperture to engage a setscrew socket androtate the setscrew against the lead connector element, thereby clampingthe connector element against an inner surface of the connector blockand ensuring electrical contact between a lead conductor of theelectrical medical lead and the circuitry of the IPG or monitor. Theattachment is reliable over long-term chronic implantation if thesetscrew is properly tightened.

Over long-term chronic implantation, it is desirable to ensure that bodyfluids do not pass through the further header aperture and headerconnector bore to the connection made between the setscrew and the leadconnector element within the connector block bore so that the IPG doesnot fail. Sealing rings are typically formed around the proximalconnector assembly of the electrical medical lead that seal against theheader connector bore upon insertion of the lead connector assembly intothe header connector bore. Sealing or closing the further headeraperture from fluid intrusion is a somewhat more difficult problem tosolve, and various methods have been developed and implemented over theyears.

In one approach, disclosed in U.S. Pat. No. 4,105,037, for example, thefurther header aperture is filled with a quantity of liquid siliconemedical adhesive after the setscrew is tightened against the leadconnector element. It is then necessary to wait for the silicone rubberadhesive to solidify before the implantation can be completed. Thisapproach requires considerable care to complete without leaving voidsand bubbles in the applied adhesive that body fluids can pass through.The cured silicone rubber adhesive is also difficult to remove afterchronic implantation to be able to replace the electrical medical leador the IPG or monitor.

In a further approach, various removable plugs have been proposed tofill the further header aperture to seal the setscrew and connectorblock from body fluids after the setscrew is tightened against the leadconnector element as disclosed in U.S. Pat. Nos. 3,822,707, 3,908,668,4,072,154, and 4,180,078, for example. The plug employed in the '154patent is formed of a resilient silicone rubber or other biocompatibleelastomer or elastomeric compound having an annular ring that fits intoan annular groove of the further header aperture to retain the plugwithin the further header aperture. As shown in U.S. Pat. Nos.4,141,752, 4,262,673 and 4,316,471, the plug is rigid like the header,and a resilient, silicone rubber, sealing O-ring is trapped andcompressed between the plug sidewall and the further header aperture asthe plug is inserted and tightened.

Fitting very small rigid or flexible plugs into the further headeraperture is difficult, and they can be dislodged and lost during theprocedure. The setscrew used to connect the electrode to the stimulatoris quite small and if a plug is used to seal the setscrew, the plug isalso quite small. From time to time, one or the other is lost on or nearthe operating table. In addition, due to their small size, both arequite difficult to handle directly by hand, which is quite undesirableduring surgery. It is also not possible to immediately confirm that afluid tight seal has been achieved.

In the '752 patent, the electrically conductive, metal setscrew isembedded within and physically attached to the plug so that the setscrewand plug screw are simultaneously rotated into the aligned setscrewconnector bore and further header aperture by a tool engaging the plugto rotate it. The exterior surface of the plug is formed with a metalcap having a Phillips type cruciform opening that is engaged by a driverto rotate the integral cap and setscrew to tighten or loosen it. Again,the combined plug and setscrew can be mishandled, and it is also notalways possible to confirm that a fluid tight seal has been achieved.

In U.S. Pat. No. 4,461,194, it is proposed to provide a tool forinserting a setscrew and a plug into the aligned threaded bore andfurther header aperture, respectively. The tool includes an elongatedhandle having a first wrench at one handle end and a second wrench atthe other handle end. A rigid cap and a sealing member made of a softsealing implantable medical grade elastomeric material are positioned onthe first wrench with the rigid cap nearest the handle. A setscrew ispositioned on the end of the wrench adjacent the sealing member and ispreferably held on the end of the first wrench with a medical gradeadhesive. The rigid cap is frictionally held in a predetermined spacedrelationship from the setscrew, preferably, by a cylindrical tubefrictionally engaging the periphery of the cap and fixedly attached tothe handle portion. The rigid cap and the second wrench are designedsuch that the second wrench is used to drive the cap and compress thesealing member, thus providing a leak-proof seal. Again, there is achance that the setscrew and plug will not remain on the handle duringthe procedure.

In a further approach that is in common use at the present time, thesetscrew is partly screwed into the setscrew connector bore duringmanufacture. A pre-formed sealing member or element, typically referredto as a septum or a grommet, fills the header aperture aligned with thesetscrew aperture (referred to in this context as a “grommet aperture”)as disclosed, for example, in the above-referenced '668 patent and inU.S. Pat. Nos. 4,010,762, 4,479,489, 4,932,409, 5,207,218, 5,522,861,and 5,989,077. The pre-formed grommet is typically formed of flexiblesilicone rubber molded into a disc-shape having an inner end walldisposed toward the connector block and an outer end wall exposed tobody fluids and tissue during implantation and a sidewall joining theend walls. A slit is typically formed through the grommet extendingbetween the inner and outer end walls so that a hex wrench can be passedfrom the outer end wall through the pre-formed slit to engage thesetscrew socket and rotate the setscrew. The pre-formed slit is expectedto reseal and prevent fluid migration therethrough after the setscrew iswithdrawn due to the soft pliant nature of the silicone rubber. At alater time, the IPG or monitor can be surgically exposed, and the hexwrench can be inserted through the pre-formed slit in the penetrablegrommet to engage and rotate the setscrew away from the lead connectorelement, thereby releasing the connector element so that the leadconnector assembly can be detached and withdrawn from the headerconnector bore.

Connector headers employing such penetrable grommets were typicallyfabricated as described in the above-referenced '668 patent to form anon-conductive, header body adhered to the IPG housing and about theelectrically conductive components. The feedthrough pin(s) extendingfrom the IPG housing were connected with the connector block(s), anddisposable plug(s) or sleeve(s) were fitted into the connector blockbore(s) to extend away from the connector block(s), a penetrablegrommet(s) was fitted to extend from the setscrew(s), and a mold wasfitted about the sub-assembly. The mold was filled with a biocompatibleliquid epoxy, and the mold and disposable plug(s) or sleeve(s) wereremoved when the epoxy hardened to form a non-conductive, header bodyabout the electrically conductive components. In the above-referenced'489 patent, it appears that a header grommet aperture was formed in theconnector header body perhaps by use of a disposable plug, and thepre-formed penetrable grommet was adhered within the header grommetaperture employing an adhesive. The use of adhesive to retain theflexible plug is also suggested in the above-referenced '154 patent.

The penetrable grommet disclosed in the above-referenced '668 patent wasquite large in diameter and thickness and was retained in place bymolding the epoxy header body about the grommet to fit around anoutwardly projecting ridge. Good adhesion was achieved between the epoxyheader body and the silicone rubber grommet because of the ability toform such a mechanical interlock and because the thermosetting epoxyadhered well with silicone rubber as it solidified. Moreover, epoxyconnector bodies remain relatively rigid and dimensionally stable duringchronic implantation, so that separation and loss of adhesion does notreadily occur. The use of the penetrable grommet simplifiedmanufacturing and solved many of the problems associated with use ofseparate caps or plugs that the physician had to use to fill the furtherheader aperture as described above, but other problems were observedover time.

The in situ molding process for forming the connector header body doesnot lend itself to mass production, since it does not involve use ofinterchangeable parts, and because the steps have to be done carefullyand slowly. Bubbles, voids, surface blemishes and other defects canoccur requiring rework or scrapping of the product. These drawbacksbecame more apparent and difficult to resolve as connector headers werereduced in size and incorporated increasing numbers of connector blocksand feedthroughs.

Consequently, a pre-formed, electrically insulating, dielectric, headerbody was developed as described in commonly assigned U.S. Pat. Nos.4,142,532, 4,154,248, 4,182,345, and 4,226,244, and in U.S. Pat. No.4,445,511, having pre-formed cavities, bores, and apertures foraccommodating the connector block(s), feedthrough pin(s), pre-formedpenetrable grommet(s), fixation mechanisms for attachment to the IPG ormonitor housing, and for providing the header connector bore(s). Variousattachment techniques for attaching the connector header body to thehermetically sealed housing involving use of mechanical lockingcomponents and adhesive backfilling of voids are also disclosed in thesepatents.

The pre-formed connector body can be formed of polyurethanes, e.g.,PELLETHANE® urethane and TECOTHANE® urethane sold by Upjohn, Inc., apolysulfone, e.g., UDEL® polysulfone sold by Union Carbide, Inc.,polymethylpentene, e.g., TPX® polymethylpentene sold by Mitsui andCompany, polyvinylidene fluoride, e.g., KYNAR® polyvinylidene fluoridesold by the Allied Chemical, and ethylenechlorotrifluoroethylene, e.g.,HALAR® ethylenechlorotrifluoroethylene sold by the Allied ChemicalCorporation. Currently, pre-formed connector bodies used by the assigneeof the present invention are injection molded of TECOTHANE® urethanebecause of its recognized biocompatibility and availability for use inIMDs.

The use of the pre-formed header body and these assembly techniquessimplified assembly, reduced rework, and reduced chronic failure rate.Over time, such IPGs and monitors employing pre-formed header bodyfabrication techniques have been advantageously increased incapabilities and longevity while being reduced in thickness, height, andwidth, which define the displaced volume, and in weight. The reductionin the volume of the connector header has been achieved in part bysubstantially reducing the dimensions of the pre-formed penetrablegrommets fitted into correspondingly reduced size header grommetapertures. However, problems have been observed as the size of thepre-formed penetrable grommets and the corresponding header grommetapertures have been reduced.

The passage of the hex wrench through the pre-formed slit is intended todisplace, rather than remove the silicone rubber along the slit.However, the possibility of coring the pre-formed penetrable grommet bythe hex wrench inserted through the pre-formed slit increases as thediameter of the pre-formed penetrable grommet is decreased. Even theproper insertion of the hex wrench through the pre-formed slit can causecoring of the silicone rubber and deposition of the cored siliconerubber within the setscrew socket. The cored slit cannot properly seal,and the silicone rubber lodged within the setscrew socket can blockinsertion of the hex wrench into the socket. The penetrable grommet mustbe designed to yield so as to move the displaced silicone rubber out ofthe way as the hex wrench is advanced through the slit.

As disclosed in the above-referenced '489 and '928 patents, a yieldspace between the inner surface of the grommet and the setscrew isprovided to accommodate the silicone rubber of the grommet that isdisplaced inward by the advancing hex wrench. In the '928 patent, arigid, ring-shaped, stiffener element is also embedded within thepre-formed grommet surrounding the yield space to stiffen the grommetand lessen the possibility of damage to the grommet by insertion of thehex wrench. Whether or not such an approach has merit, fabrication ofsuch a pre-formed grommet with a rigid, ring-shaped, stiffener elementmay be difficult.

Even the proper insertion of the hex wrench through the pre-formed slitcan also cause loss of adhesion of the grommet to the grommet aperturewall surrounding it unless the penetrable grommet is designed to yieldand distribute stresses away from the grommet aperture wall as the hexwrench is advanced through the slit.

The mutual area of contact between the sidewalls of each pre-formedpenetrable grommet and the header grommet aperture is necessarilyreduced in order to reduce the overall volume of the connector header.The silicone rubber of the pre-formed penetrable grommet does notinherently adhere well with the material, particularly, TECOTHANE®urethane, of the pre-formed connector header body. Forming one or moreretention ridge in the header grommet aperture sidewall to engage thesidewall of the silicone rubber grommet as shown in the above-referenced'928 patent, for example, is difficult if not impossible due to theinjection molding of the pre-formed connector body from TECOTHANE®urethane.

Consequently, the low adhesion and reduced mutual area of contactbetween the grommet and header grommet aperture sidewalls hasnecessitated the use of a medical grade adhesive applied to between thegrommet and header grommet aperture sidewalls before the pre-formedgrommet is inserted into the header grommet aperture. The application ofminute amounts of adhesive complicates assembly, and non-destructivetesting of the resulting adhesion strength is difficult to accomplish.The applied adhesive can also intrude into the interior yield spaceand/or the socket of the setscrew. For these reasons, it would bepreferable to eliminate use of adhesive to maintain the pre-formedgrommet within the header grommet aperture

Other problems have been observed with the use of silicone rubber toform such penetrable grommets and urethanes to form connector headerbodies.

The epoxy or urethane connector header body and the silicone rubbergrommet are both translucent and substantially colorless or of a slightcolor such that there is little visible contrast therebetween, renderingit difficult to visually distinguish a penetrable grommet from thesurrounding connector header body and to locate the pre-formed slit.Physicians at times inadvertently insert the hex wrench through thepre-formed slit offset from the central axis of the penetrable grommetor at an improper angle and then have to move the hex wrench about orwithdraw and reinsert it to properly seat the hex wrench tool end intothe setscrew socket to rotate it. This could cause damage to thepenetrable grommet compromising the ability of the pre-formed slit toreseal.

Moreover, the silicone rubber material is “sticky” and tends to adhereto itself across the pre-formed slit with aging so that the pre-formedslit tends to heal. After prolonged storage or chronic implantation, itbecomes more difficult to insert a hex wrench through the pre-formedslit without coring or dislodging the penetrable grommet from the headergrommet aperture. Sometimes, the pre-formed slit will not open at all,and the silicone rubber or the penetrable grommet is “punched out” whenthe hex wrench is advanced against it and into the underlying setscrewsocket. The setscrew socket becomes plugged by the silicone rubber, andthe penetrable grommet no longer seals.

It has also been found that connector header bodies formed of TECOTHANE®urethane exhibit cold flow or creep at points or surfaces where pressureis applied chronically. It has been observed that adhesion is lostbetween the grommet and header grommet aperture sidewalls when thegrommet exerts pressure over time against the header grommet aperturesidewall causing expansion of the header grommet aperture diameter.

In addition, the TECOTHANE® urethane connector header body becomesslightly less rigid and dimensionally stable during chronic implantationin body fluids thereby aggravating the cold flow problem and negativelyaffecting adhesion with the silicone rubber grommet over time that canlead to spontaneous dislodgement of the grommet. Moreover, the weakenedadhesion can be overcome if a replacement procedure requiring insertionof the hex wrench through the grommet slit occurs, and the grommet canbe dislodged upon withdrawal of the hex wrench. It would be desirable toeliminate or accommodate the cold flow dimensional instability of theconnector header body.

Further problems arise as the setscrews and connector blocks areminiaturized. Setscrews are typically formed without a head or“headless” having a uniform outer diameter extending between the socketend and the working or contact end. The setscrew working end istypically closed or solid, and the setscrew socket is a fraction of thelength of the setscrew, limiting the depth of the setscrew socket thatcan be engaged by the hex wrench. As noted above, it can be difficult tolocate such a shallow setscrew socket with the hex wrench, and adhesiveand/or dislodged silicone rubber can block the shallow setscrew socket.

Size and fit tolerances of the setscrew thread and the threaded boremust be dictated to ensure that the setscrew can be easily rotated andtightened using a specified low torque applied to the setscrew tool orhex wrench. One problem that has occurred due to the tolerances and theinvolves the inappropriate positioning during manufacture or spontaneousmovement of the setscrew within the threaded bore due simply to handlingand shipment that cannot be observed when the setscrew is covered by thepenetrable grommet. It has been observed that the setscrew caninadvertently migrate and intrude into the connector block bore to blockinsertion of a lead connector element into the connector block bore. Thephysician inserting the connector lead element into the connector blockbore may incorrectly assume that it is properly inserted and tightendown the setscrew without making contact, resulting in a connectionfailure that may or may not be detected at the time of implantation.

In addition, the headless setscrew must be longer than the diameter ofthe connector block bore to prevent it from being unintentionallyadvanced all the way through the threaded bore and released into theconnector bore. Moreover, tubular lead connector elements in currentcommon use have a range of diameters, and the axially aligned connectorheader bores and connector block bores are provided in a correspondingrange of diameters. Consequently, it has been necessary to either use aheadless setscrew longer than the largest connector block bore diameterfitted into correspondingly long threaded bore or to provide a range ofsetscrews having lengths exceeding the connector block bore diameters.It would be desirable to simplify specification and costs of setscrewsby employing a common setscrew for all such connector blocks.

Therefore, despite the improvements that have been made in connectorheaders over the years, problems remain to be solved in the design andfabrication of connector headers of the type employing penetrablegrommets disposed in header grommet apertures overlying fasteners, e.g.,setscrews, employed to attach lead connector elements with connectorblocks of the connector header.

SUMMARY OF THE INVENTION

The preferred embodiments of the present invention incorporate a numberof inventive features that address the above-described problems withpenetrable grommets that may be combined with other features of thepreferred embodiments or advantageously separately employed in connectorheaders of IMDs.

The connector headers for an IPG or monitor illustrated in the preferredembodiments incorporate a penetrable grommet entrapped within a headergrommet aperture of a pre-formed header body to provide a fluid seal ofa fastener, e.g., a setscrew within a threaded bore, of a connectorblock without the use of adhesive between the penetrable grommet and theheader grommet aperture. An inner end wall of the disc-shaped penetrablegrommet is disposed to face the setscrew, an outer end wall of thedisc-shaped penetrable grommet is disposed to face outward in contactwith body fluids, and a grommet sidewall bears against the sidewall ofthe header grommet aperture. Preferably, a pre-formed, resealable, slitextends axially between the outer and inner end walls of thedisc-shaped, penetrable grommet.

In accordance with one aspect of the present invention, a ring-shapedretainer having a central bore that a tool, e.g., a hex wrench, can bepassed through is disposed against an annular portion of the outer endwall and is affixed to an annular portion of the header body surroundingthe annular portion of the outer end wall. Advantageously, substantiallythe full length of the pre-formed slit is disposed within the headergrommet aperture below the ring-shaped retainer so that the contactbetween the grommet sidewall and the grommet aperture sidewall tends toprovide a uniform pressure to the pre-formed slit between the outer andinner end walls of the disc-shaped, penetrable grommet.

The central bore of the ring-shaped retainer is aligned with thepre-formed slit and provides a visible target for precisely aligning andinserting the setscrew tool through the slit into operative engagementwith the setscrew. Furthermore, the ring-shaped retainer can besubstantially colorless or can be formed of a colored materialcontrasting from the substantially colorless or slightly coloredconnector header body and providing a visual target for preciselyaligning and inserting the tool through the central bore and the slitinto operative engagement with the setscrew.

In accordance with an aspect of the present invention, the cylindricalsidewall of the disc-shaped, penetrable grommet is formed having anirregular surface comprising a plurality of peaks and valleys thatmaintains fluid sealing contact with the cylindrical sidewall of thetubular header grommet aperture without adhesive therebetween. Thenominal peak-to-peak outer diameter of the grommet can be specified toexceed the nominal inner diameter of the grommet aperture sidewall suchthat a low pressure interference fit is achieved upon insertion of thedisc-shaped penetrable grommet into the header grommet aperture thatreduces pressure applied against and resulting cold flow of the grommetaperture sidewall. Advantageously, the dimensional tolerances of thepeak-to-peak diameter of the disc-shaped penetrable grommet and theinner diameter of the cylindrical sidewall of the tubular header grommetaperture can be relaxed to lower costs and to account for any changes inthe nominal inner and outer diameters over chronic implantation. A low,uniform, interference pressure is attained over a wide tolerance uponassembly that is maintained even if the inner diameter of thecylindrical sidewall of the tubular header grommet aperture changes overextended time periods.

Preferably, the irregular surface comprises a plurality of sealing ringsextending around the periphery of the grommet sidewall ensuring fluidsealing during chronic implantation. In addition, the sealing ringsabsorb stresses imposed when the setscrew tool is inserted through thepre-formed slit into engagement with the setscrew socket and moves thesilicone rubber of the penetrable grommet outward against the grommetaperture sidewall.

Preferably, a yield space is formed in the inner end wall of thedisc-shaped penetrable grommet to accommodate silicone rubber displacedinward by the advancement of the tool through the slit into the setscrewsocket without stressing the attachment of the ring-shaped retainer tothe connector header body.

In accordance with a still further aspect of the invention, thedisc-shaped penetrable grommet is preferably formed of silicone rubberand an additive that diminishes the tackiness or stickiness of themutually contacting silicone rubber surfaces that are formed by the slitmade between the outer and inner end walls of the disc-shaped penetrablegrommet. In this way, the formulated silicone rubber and additivediminishes the tendency to heal the slit over chronic implantation time.

In accordance with yet another aspect of the invention, the disc-shapedpenetrable grommet is preferably formed of substantially colorlesssilicone rubber and an additive that pigments the penetrable grommet toprovide visual contrast to the surrounding connector body material.

Preferably, the additive comprises titanium dioxide in a concentrationof up to about 2% by weight. The titanium dioxide additiveadvantageously also colors the disc-shaped penetrable grommet opaque andthereby renders it more visible with respect to the transparent ortranslucent connector header body so that accurate insertion of the toolthrough the grommet slit is aided.

In accordance with a still further aspect of the invention, the setscrewis inhibited from being advanced during assembly or spontaneously intothe connector block lumen intended to receive the lead connectorelement. The setscrew socket end engaged by the tool is preferablyenlarged in diameter with respect to the threaded bore to limitadvancement of the setscrew therein. The setscrew socket end is alsopreferably funnel shaped to eliminate a sharp cutting edge, to guide asetscrew tool end into the socket, and to provide a space accommodatingany displaced silicone rubber of the penetrable grommet. The setscrewsocket advantageously extends for substantially the full length of thesetscrew to maximize setscrew socket depth and mutual contact area ofthe setscrew and the setscrew tool. In one embodiment of this aspect ofthe invention, the setscrew is shaped to have an enlarged diametersetscrew socket end. In another embodiment of this aspect of theinvention, the setscrew socket end of an otherwise “headless” setscrewis preferably enlarged in diameter by a ring molded around the setscrewat the setscrew socket end to provide the enlarged diameter setscrewsocket end.

In one preferred embodiment of this aspect of the invention, a setscrewretention space is provided between the inner end wall of the penetrablegrommet and the connector block enabling the retraction of the setscrewto a retracted position with the setscrew substantially disposed withinthe setscrew retention space. After assembly, a setscrew tool isinserted through the penetrable grommet into the setscrew socket torotate the setscrew. The setscrew is rotated until the enlarged diametersetscrew socket end is retracted into frictional engagement with theinner end wall of the penetrable grommet and the setscrew thread issubstantially retracted out of the threaded bore, and the setscrew toolis withdrawn. The frictional engagement and retraction of the setscrewthread stabilizes the setscrew in the retracted position and inhibitsspontaneous migration of the setscrew through the threaded bore into theconnector block bore.

During implantation, a setscrew tool is inserted through the grommetslit into the setscrew socket and rotated to advance the setscrewthreads along the threads of the threaded bore in the tighteningdirection until the setscrew working end engages the lead connectorelement. The application of the enlarged diameter setscrew socket endagainst the inner end wall of the penetrable grommet stabilizes thepenetrable grommet from being unduly pressed inward by setscrew tool andminimizes punch out and coring of the penetrable socket.

The setscrew length can be optimized to minimize the threaded borelength and the length of the setscrew retention space regardless of thediameter of the connector block bore. The pitch and number of turns ofthe mating setscrew and threaded bore threads can be selected to providemovement of the setscrew between the retracted and advanced positionswith a minimal number of turns of the setscrew tool. The setscrew andthe threaded bore can be standardized for connector blocks havingconnector bores dimensioned to receive a wide range of lead connectorelement dimensions.

This summary of the invention has been presented here simply to pointout some of the ways that the invention overcomes difficulties presentedin the prior art and to distinguish the invention from the prior art andis not intended to operate in any manner as a limitation on theinterpretation of claims that are presented initially in the patentapplication and that are ultimately granted.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of an exemplary IMD comprising a pacemakerIPG and atrial and ventricular electrical medical leads in which theinventive features of connector headers may be incorporated incombination or separately;

FIG. 2 is a perspective view of a first embodiment of the pacemaker IPGconnector header of FIG. 1 with a setscrew, penetrable grommet, andring-shaped retainer illustrated in relation to a grommet aperture andconnector block within a cavity of the connector header body;

FIG. 3 is a cross-section view taken along lines 3—3 of FIG. 2illustrating the ring-shaped retainer, the penetrable grommet within thegrommet aperture, and the connector block within the connector headerbody with the setscrew in a partially advanced position to bear againsta lead connector element within the connector bore;

FIG. 4 is a cross-section view taken along lines 3—3 of FIG. 2illustrating the ring-shaped retainer, the penetrable grommet within thegrommet aperture, and the connector block within the connector headerbody with the setscrew in the retracted position to frictionally engageagainst the grommet inner end wall to inhibit unintentional rotation andmovement to the advanced position of FIG. 3;

FIG. 5 is a perspective view of a second embodiment of the pacemaker IPGconnector header of FIG. 1 with a setscrew, penetrable grommet, and aretainer cap illustrated in relation to a grommet aperture and connectorblock within the connector header body;

FIG. 6 is a cross-section view taken along lines 6—6 of FIG. 5illustrating the retainer cap, the penetrable grommet within the grommetaperture, and the connector block within the connector header body withthe setscrew in a partially advanced position to bear against a leadconnector element within the connector bore;

FIG. 7 is a cross-section view taken along lines 6—6 of FIG. 5illustrating the retainer cap, the penetrable grommet within the grommetaperture, and the connector block within the connector header body withthe setscrew in the retracted position to frictionally engage againstthe grommet inner end wall to inhibit unintentional rotation andmovement to the advanced position of FIG. 3;

FIG. 8 is an expanded perspective view of the retainer cap of FIGS. 5–7illustrating the laterally extending retention elements in the capsidewall for gripping the connector block body when the cap sidewall isinserted into the groove surrounding the grommet aperture as shown inFIGS. 6 and 7;

FIG. 9 is an exploded perspective view of a first embodiment of asetscrew and connector block of the present invention;

FIG. 10 is a side view of the setscrew illustrated in FIG. 9;

FIG. 11 is a side cross-section view taken along lines 11—11 of FIG. 10of the setscrew illustrated in FIGS. 9 and 10;

FIG. 12 is a side view of second embodiment of a setscrew adapted to beused with the connector block illustrated in FIG. 9;

FIG. 13 is a side cross-section view taken along lines 13—13 of FIG. 12of the setscrew illustrated in FIG. 12;

FIG. 14 is an expanded side view of the penetrable grommet of thepresent invention;

FIG. 15 is an expanded perspective view of the penetrable grommet of thepresent invention.

FIG. 16 is an expanded perspective view of a further embodiment of theretainer cap of FIGS. 5–7 illustrating notches formed in the capsidewall for engagement with ridges formed in the groove when the capsidewall is inserted into the groove surrounding the grommet aperture asshown in FIGS. 6 and 7;

FIG. 17 is a detail view of a tab formed in the groove about to bereceived in a notch formed in the cap sidewall of the retainer capillustrated in FIG. 16 when the cap sidewall is inserted into thegroove;

FIG. 18 is a detail view of the tab formed in the groove received in thenotch of FIG. 17 and the application of ultrasonic energy to theretainer cap to heat and melt the thermoplastic material of the tabcontacting the cap sidewall; and

FIG. 19 is a detail view of the thermoplastic material of the tab meltedinto and filling the notch of FIGS. 17 and 18 following application ofultrasonic energy to the retainer cap.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

In the following detailed description, references are made toillustrative embodiments of methods and apparatus for carrying out theinvention. It is understood that other embodiments can be utilizedwithout departing from the scope of the invention. Methods and apparatusare described for attaching lead connector elements of electricalmedical leads received within connector bores of connector headersattached to hermetically sealed enclosures of IPGs or monitors of any ofthe types known in the art.

For example, a pacemaker IPG 100 is illustrated in FIG. 1 adapted to beattached to a bipolar atrial endocardial pacing lead 116 and attached toa bipolar ventricular endocardial pacing leads 118 extending in atransvenous pathway from the subcutaneous site of implantation of theIPG 100 into the right atrium and right ventricle of a patient's heart16, respectively. The bipolar atrial endocardial pacing lead 116comprises an elongated lead body enclosing a pair of electricallyinsulated lead conductors each extending from a connector element ofproximal lead connector assembly 122, e.g., a connector pin 123 and aconnector ring 125, and one of distal tip and ring pace/sense electrodes121 and 120, respectively. Similarly, the bipolar ventricularendocardial pacing lead 118 comprises an elongated lead body extendingbetween proximal lead connector assembly 122, e.g., a connector pin or aconnector ring (obscured in the view), and one of distal tip and ringpace/sense electrodes 129 and 128, respectively. The bipolar endocardialpacing leads 116 and 118 can take any of the forms known in the art ofpacing and cardioversion/defibrillation lodged in heart chambers orcardiac vessels or disposed on the epicardial surface of the heart 16 asis known in the art. Typically, in bipolar cardiac pacing leads, oneelectrical conductor extends between a proximal connector pin, e.g.,connector pin 123, and a distal tip electrode, e.g., pace/senseelectrode 121, and a second electrical conductor extends between aconnector ring distal to the proximal connector pin, e.g., connectorring 125, and the ring electrode, e.g., pace/sense electrode 120.

The pacemaker IPG 100 comprises a hermetically sealed housing 102 thatencases a battery and circuitry and electrical components powered by thebattery to process atrial and ventricular cardiac signals and generateatrial and/or ventricular pacing pulses to synchronously pace the atriaand ventricles as needed in a manner well known in the art. Thepacemaker IPG 100 also comprises a connector header 106 formed of forexample, a dielectric header body 110 injection molded of TECOTHANE®urethane as described above. The header body 110 is formed having anelongated header connector bore 112 for receiving the bipolar atriallead connector assembly 122 and a ventricular lead header connector bore114 for receiving the bipolar ventricular lead connector assembly 124.

In FIGS. 1 and 2, two pin connector assembles 140 and 142 incorporatingaspects of the present invention that can be accessed from one side 130of the pre-formed header body 110 are depicted. It will be understoodthat two similar ring connector assemblies that are obscured from viewby the pre-formed header body 110 can be accessed from the opposite side132 of the pre-formed header body 110. It will be understood that all ofthe pin and ring connector assemblies could be oriented to be viewed andaccessed from the same side 130 or 132. Alternatively, at least the pinand/or ring connector assembly for connecting the connector pin and/orring of the bipolar atrial pacing lead 116 could be accessed from thetop 134 of the pre-formed header body 110.

In the illustrated embodiments, the atrial header connector bore 112 andassociated pin and ring connector assemblies are disposed above theventricular header connector bore 114 and its associated pin and ringconnector assemblies in this particular embodiment. Alternatively, theatrial and ventricular header connector bores 112 and 114 and associatedpin and ring connector assemblies could be disposed in side-by-siderelation. The number of header connector bores of the connector header106 and the number of connector assemblies associated with each headerconnector bore can vary considerably depending upon the type of IPG ormonitor and electrical medical leads selected to be coupled to theconnector header 106.

It will be understood that the ring and pin connector block borediameters, the spacing of the pin and ring connector blocks, and thediameters along the lengths of the header connector bores 112 and 114are selected to conform to a proprietary standard or an industryrecognized standard, e.g., the IS-1 standard. For example, Medtronic,Inc. presently manufactures ICD IPGs with four basic connector designs,designated configurations “B”, “C”, “D”, and “E”. The “B” configurationincludes three 6.5 mm connector bores for receiving high voltageelectrical lead connectors of the type used to couple tocardioversion/defibrillation electrodes and one IS-1 compatible 3.2 mmin-line electrical connector bore for receiving an IS-1 electrical leadconnector of the type generally used to couple to cardiac pacing andsensing electrodes. The “C” configuration includes a single 3.2 mm“DF-1” connector bore for receiving high voltage electrical leadconnectors used to couple to cardioversion/defibrillation electrodes anda single IS-1 connector bore. The “D” configuration includes three DF-1connector bores and one IS-1 connector bore. The “E” configurationincludes two 6.5 mm connector bores and two 5 mm connector bores forreceiving electrical lead connectors used to couple to individualcardiac pacing and sensing electrodes.

Regardless of the number and orientation of the four connectorassemblies 140, 142 etc., each comprises a connector block 150, asetscrew 160, a penetrable grommet 180 and a ring-shaped retainer 200arranged as shown in FIGS. 2–4. The advanced and retracted positions ofthe setscrew 160 with respect to the connector block 150 and thepenetrable grommet 180 are depicted in FIGS. 3 and 4. In thisembodiment, a tubular grommet aperture 136 having a cylindrical grommetaperture sidewall 137 extends from side 130 into the header body 106transverse to the axis of header connector bore 114. An annular seat 138is formed around the grommet aperture 136. The ring-shaped retainer 200is preferably formed of a dielectric thermoplastic material and is sizedin outer diameter to be fitted into the annular seat 138 and thermallywelded to the material of the connector header body 110. The annularseat 138 preferably includes an annular ridge of other enhancement thatfacilitates thermal bonding of the ring-shaped retainer 200 to theannular seat as described further below.

In the exploded view of the components of the connector assembly 142depicted in FIG. 2, one such connector block 150 fitted into a cavitywithin the pre-formed header body 110 is exposed for view though thegrommet aperture 136. Each connector block 150 is electrically connectedto the circuitry within the housing 102 by a connector pin of afeedthrough (not shown) that is mounted to extend through the wall ofhermetically sealed housing 102 in a manner well known in the art. Inthe particular illustrated embodiments, atrial and ventricular pin andring connector blocks 150 are disposed and spaced apart in cavitiesalong the respective atrial and ventricular header connector bores 112and 114 by a spacing corresponding to the spacing between the connectorpins and rings (not shown) of the atrial and ventricular lead connectorassemblies 122 and 124.

In reference to FIG. 9, each connector block 150 is formed of stainlesssteel, for example, and has a threaded bore 152 intersecting a connectorblock bore 154 such that the connector block bore 154 extendstransversely to the threaded bore 152. A spiral thread 156 is formed inthe threaded bore 152. The connector block bore 154 has a bore diameter156 sized to receive a lead connector pin or ring, and each connectorblock bore 152 is axially aligned with the axis of one of the headerconnector bores 112 or 114. Typically, the bore diameter 156 of aconnector block 150 employed to attach a lead connector pin is smallerthan the bore diameter 156 of a connector block 150 employed to attach alead connector ring.

In reference to FIGS. 9–11, a first embodiment of a setscrew 160 adaptedto be threaded into the threaded bore 152 is depicted. The setscrewextends between a setscrew working end 162 and a setscrew socket head164, and a spiral thread 166 is formed around the circumference thereof.The spiral thread 166 corresponds dimensionally and in pitch to thespiral thread 158 or the threaded bore 152 so that the setscrew 160 canbe moved between a retracted position depicted in FIG. 3 and an advancedposition depicted in FIG. 4. The setscrew socket 170 can take any shapethat can receive a setscrew tool, e.g., a hexagonal shape that is sizedto receive a hex wrench setscrew tool.

The setscrew socket head 164 is enlarged in diameter surrounding theopening to the setscrew socket 170 with respect tot eh diameter of thethreaded bore 152. The setscrew 160 is inhibited by the enlargeddiameter setscrew socket head 164 from being advanced during assembly orspontaneously beyond the advanced position depicted in FIG. 4 and allthe way through the threaded bore 152 and into the connector block lumen154 intended to receive the lead connector element. The enlargeddiameter setscrew socket head 164 is formed with a funnel-shaped opening176 that guides a hex wrench passed through the penetrable grommet 180into the setscrew socket 170. The funnel shape also eliminate a sharpcutting edge at the opening of the setscrew socket 170 that could shearany silicone rubber of the penetrable grommet 190 that is pushed intothe socket opening by the advancing hex wrench. The funnel shape alsoprovides an annular space 178 to receive any such silicone rubber of thepenetrable grommet 190 that is pushed toward the socket opening orotherwise displaced by the advancing hex wrench.

Typical prior art setscrews are formed with a closed setscrew workingend 162 resulting in a relatively short setscrew socket. The setscrewsocket 170 advantageously extends for substantially the full length ofthe setscrew between the annular space 178 and the setscrew working end162 to maximize the depth of the setscrew socket 170 and the mutualcontact area of the setscrew socket walls and the setscrew tool insertedinto the setscrew socket 170. In accordance with the present invention,a hex wrench stop ring 174 is formed at the setscrew working end thatblocks advancement of the hex wrench all the way through the setscrewsocket 170.

The penetrable grommet 180 (shown enlarged in FIGS. 14 and 15 and inside section view in FIGS. 3 and 4) is entrapped within the headergrommet aperture 136 of the pre-formed header body 110 by the retainer200 as described further below. The penetrable grommet 180 provides afluid seal of the setscrew 160 within the threaded bore 152 of aconnector block 150 without the use of adhesive between the penetrablegrommet 180 and the header grommet aperture 136.

An inner end wall 182 of the disc-shaped penetrable grommet 180 isdisposed to face the setscrew 160, and an outer end wall 184 of thedisc-shaped penetrable grommet 180 is disposed to face outward incontact with body fluids. The outer end wall 184 preferably comprises acircular, outwardly projecting portion 188 surrounded by an annular,substantially flat or planar portion 185. A grommet sidewall 186 extendsbetween the inner and outer end walls 182 and 184 that bears against thesidewall 137 of the header grommet aperture 136.

A self-sealing passage, e.g., a pre-formed slit 190, extends axiallybetween the outer and inner end walls 182 and 184 of the disc-shapedpenetrable grommet 180. The pre-formed slit 190 preferably extendslaterally across the central axis of the disc-shaped penetrable grommet180 within the circular, outwardly projecting portion 188. Thepre-formed slit can take any of the known forms, including a single cutbisecting the central axis of the disc-shaped penetrable grommet 180 asdepicted in the above-referenced '489 patent or a Y-shaped or a crossshaped slit centered on the central axis of the disc-shaped penetrablegrommet 180.

The cylindrical sidewall 186 of the disc-shaped, penetrable grommet 180is preferably formed having an irregular surface comprising a pluralityof peaks and valleys that maintains fluid sealing contact with thecylindrical sidewall of the tubular header grommet aperture withoutadhesive therebetween. In one embodiment, the irregular surfacecomprises a corrugated surface attained by a plurality of sealingring(s) 192, 194, 196, 198 extending around the periphery of the grommetsidewall 186 ensuring fluid sealing between the grommet sidewall 186 andthe grommet aperture sidewall 137 during chronic implantation. Thenominal peak-to-peak outer diameter of the penetrable grommet 180 can bespecified to exceed the nominal inner diameter of the grommet aperturesidewall 137 such that a low pressure interference fit is achieved uponinsertion of the disc-shaped penetrable grommet 180 into the headergrommet aperture 136 that reduces pressure applied against and resultingcold flow of the grommet aperture sidewall 137. Advantageously, thedimensional tolerances of the peak-to-peak diameter of the disc-shapedpenetrable grommet 180 and the inner diameter of the grommet aperturesidewall 137 can be relaxed to lower costs and to account for anychanges in the nominal inner and outer diameters over chronicimplantation. A low, uniform, interference pressure is attained over awide tolerance upon assembly that is maintained even if the innerdiameter of the header grommet aperture 136 changes over extended timeperiods. In addition, the sealing rings 192, 194, 196, 198 absorbstresses imposed when the setscrew hex wrench is inserted through theslit 190 into engagement with the setscrew socket and moves the siliconerubber of the penetrable grommet 180 outward against the grommetaperture sidewall 137. In effect, the corrugated surface of the grommetsidewall 186 flattens against the grommet aperture sidewall 137.

A central, circular yield space 195 in one embodiment correspondingsubstantially in diameter to the diameter of the circular, outwardlyprojecting portion 188 is formed in the inner end wall 182 of thedisc-shaped penetrable grommet 180 as shown in FIGS. 3 and 4. The yieldspace 195 accommodates silicone rubber displaced inward by theadvancement of the setscrew hex wrench through the slit 190 into thesetscrew socket 170 without stressing the attachment of the ring-shapedretainer 200 to the connector header body 110.

Header body 110 is substantially colorless, which for reference ischaracterized herein as a first color. The substantially colorless,silicone rubber, penetrable grommet 180 can be difficult to visuallydistinguish from the header body 110, and the pre-formed slit 190 canheal over time. The disc-shaped, penetrable grommet 180 is thereforepreferably formed of silicone rubber and an additive that diminishes thetackiness or stickiness of the mutually contacting silicone rubbersurfaces that are formed by the slit 190 made between the outer andinner end walls 182 and 184. In this way, the formulated silicone rubberand additive diminishes the tendency to heal the slit 190 over chronicimplantation time. The additive additionally or alternatively, colorsthe substantially colorless silicone rubber to provide visual contrastto the surrounding connector body material.

Preferably, the additive comprises titanium dioxide in a concentrationof up to about 2% by weight. The titanium dioxide additiveadvantageously also colors the disc-shaped penetrable grommet 180 opaqueand thereby renders it more visible with respect to the transparent ortranslucent connector header body 110 so that accurate insertion of thesetscrew hex wrench through the grommet slit 190 is aided.

In the embodiment of the invention depicted in FIGS. 2–4, thering-shaped retainer 200 is formed of a thermoplastic material in theshape of a washer having retainer inner and outer annular sides 202 and204 and a central opening 210. An outer band of the inner annular side202 is thermally welded to the annular portion or seat 138 of the headerbody 110 as shown in FIGS. 3 and 4 after the setscrew 160 is screwedinto the threaded bore 152 and the penetrable grommet is fitted into thegrommet aperture 136. The thermal welding can be accomplished employingultrasonic welding techniques or heat staking techniques.

Ultrasonic welding techniques of the type described in theabove-referenced Publication No. 2003/0040780 may be employed to effectthe thermal welding. Ultrasonic energy delivered by a shaped ultrasonichead or horn to two thermoplastic pieces to be joined vibrates thepieces resulting in heat energy that melts a mass of the thermoplasticmaterial in the area of mutual contact. In this regard, an outer band ofthe inner annular side 202 and the annular portion or seat 138 of theheader body 110 are preferably configured to enhance mutual melting andthermal bonding without appreciably distorting the external appearanceof the ring-shaped retainer 200. Such enhancement can include shapingthe outer band of the inner annular side 202 and the annular portion orseat 138 to matingly engage through a tongue and groove joint, a stepjoint or a shear joint or the like. Or, a sharp edged annular ridge canbe formed extending away from the outer band of the inner annular side202 or the annular portion or seat 138 of the header body 110 so that anedge contact is made when the outer band of the inner annular side 202is applied against the annular portion or seat 138. In this way, theultrasonic energy applied to the outer annular side 204 by the shapedhead or horn of an ultrasonic generator concentrates at the line orlines of contact and heat is generated to cause melting and adhesionupon cooling.

After thermal welding of the ring-shaped retainer to the annular portionor seat 138 of the header body 110, an inner band of the inner annularside 202 bears against the annular, substantially flat or planar portion185 of the grommet outer end wall 184 to hold the penetrable grommet 180in the grommet aperture 136. The circular, outwardly projecting portion188 of the penetrable grommet 180 extends through the circular centralopening 210 so that the slit 190 can be accessed.

The central bore 210 of the ring-shaped retainer 200 is aligned with thepre-formed slit 190 and provides a visible target and guide forprecisely aligning and inserting the hex wrench through the centralopening 210, the slit 190, the central, circular yield space 195, andinto the setscrew socket 170. The ring-shaped retainer 200 can besubstantially colorless or can be formed of a colored materialcontrasting from the substantially colorless connector header body 110and providing a more visible target and guide. The funnel shaped opening176 of the setscrew socket 170 also assists in guiding the hex wrenchinto the socket 170 without shearing silicone rubber from the penetrablegrommet 180.

Referring to FIGS. 3 and 4, a setscrew retention cavity or space 220 isprovided between the inner end wall 182 of the penetrable grommet 180and the connector block 150 enabling the retraction of the setscrew 160to a retracted position depicted in FIG. 3 with the setscrew 160substantially disposed within the setscrew retention space 220. Afterassembly, a setscrew hex wrench is inserted through the penetrablegrommet slit 190 into the setscrew socket 170 to rotate the setscrew 160to back it out of the threaded bore 152. The setscrew 160 is backed outfrom the position depicted in FIG. 4 to the position depicted in FIG. 3until the enlarged diameter setscrew socket end 164 is in frictionalengagement with an annular portion of the inner end wall 182 of thepenetrable grommet 180 surrounding the circular yield space 195. Thesilicone rubber of the penetrable grommet 180 is displaced outward adistance 222, and the setscrew spiral thread 166 is substantiallyretracted out of engagement with the spiral thread 158 or the threadedbore 152. The setscrew hex wrench is withdrawn, and the frictionalengagement and retraction of the setscrew thread 166 stabilizes thesetscrew 160 in the retracted position of FIG. 3 and inhibitsspontaneous migration of the setscrew 160 through the threaded bore 152and into the connector block bore 154. The finished IPG 100 is storedand shipped with all setscrews 160 in the retracted position of FIG. 3.

The setscrew length can be optimized to minimize the threaded borelength and the length of the setscrew retention space 220. The pitch andnumber of turns of the mating setscrew and threaded bore threads 166 and158 can be selected to provide movement of the setscrew 160 between theretracted and advanced positions with a minimal number of turns of thesetscrew hex wrench. The setscrew 160 and the threaded bore 152 can bestandardized for connector blocks having connector bores dimensioned indiameter 224 to receive a wide range of lead connector elementdimensions because advancement of the setscrew 160 completely throughthe threaded bore 152 is prevented when the enlarged diameter setscrewhead contacts the connector block 150.

It should be noted that the full length of the resealable slit 190 isdisposed within the grommet aperture 136 below the ring-shaped retainer200 bearing against the annular portion 185 of the outer end wall 182 ofthe penetrable grommet 180. Thus, a substantially constant compressionforce is applied across the slit 190 from the inner end wall 182 to theouter end wall 184 due to the interference fit and slight compression ofthe rings 192, 194, 196, 198 of the grommet sidewall 186 against thecylindrical grommet aperture sidewall 136. Therefore, the tendency ofprior art resealable slits to open and admit fluids due to an unevenapplication of compressive force, particularly diminished compressiveforce at the outer end wall, is minimized.

As noted above, the IPG 100 is shipped with all setscrews 160 in theretracted position of FIG. 3. During implantation, a setscrew hex wrenchis inserted through the grommet slit 190 into the setscrew socket 170and rotated to advance the setscrew spiral thread 166 along the spiralthread 158 of the threaded bore 154 in the tightening direction untilthe setscrew working end 162 engages a lead connector element insertedthrough the connector block bore 154. It is not possible to tighten thesetscrew 160 any further once the enlarged diameter setscrew socket head164 contacts the connector block 150. Therefore it is not possible toaccidentally advance the setscrew fully into the connector block bore154.

When a hex wrench is inserted through the resealable slit 190, itdisplaces the silicone rubber of the penetrable grommet 180 laterally toeffectively flatten the grommet sidewall 186 and inward into thecircular yield space and the annular space 178. Shearing of siliconerubber and plugging of the setscrew socket 170 is avoided.

A further setscrew 160′ that can be substituted for the setscrew 160 inany of the embodiments of the invention is depicted in FIGS. 12 and 13.In this embodiment of this aspect of the invention, the setscrew socketend 164 is enlarged in diameter by a ring 165 molded around the setscrewsocket end 164.

Further embodiments of a ring-shaped retainer are illustrated in FIGS.5–8 and 16–19, wherein the connector assemblies 240 and 242 eachcomprises a connector block 150, a setscrew 160, 160′, a penetrablegrommet 180, and a ring-shaped retainer formed in the shape of aretainer cap 250, 250′, 250″. As in the embodiment of FIGS. 1–3, thetubular grommet aperture 136 having a cylindrical grommet aperturesidewall 137 extends from side 130 into the header body 106 transverseto the axis of header connector bore 114. In this embodiment, an annularretention groove 234, 234′ is formed around the grommet aperture 136whereby a ring 236 of the thermoplastic material of the header body 110is provided between the annular retention groove 234, 234′ and thegrommet aperture sidewall 137.

The retainer cap 250, 250′, 250″ is preferably formed of metal, e.g.,stainless steel, having an annular cap end wall 252 surrounding acentral cap opening 256 and a retainer cap sidewall 254 at the outerperiphery of the annular cap end wall 252. The annular cap end wall 252and the retainer cap sidewall 254 are preferably relatively thin.

In assembly, the connector block 150 is fitted into the connector blockcavity, the setscrew 160, 160′ is threaded into the threaded bore 152,and the penetrable grommet 180 is inserted into the grommet aperture136. The retainer cap sidewall 254 is inserted into the annularretention groove 234, 234′ so that the annular cap end wall 252 fitsagainst the annular portion 185 of the grommet outer end wall 184, andthe circular, outwardly projecting portion 188 projects outward throughthe central cap opening 256. The advanced and retracted positions of thesetscrew 160 with respect to the connector block 150 and the penetrablegrommet 180 are depicted in FIGS. 6 and 7, and all of theabove-described aspects of the invention can be realized in thisembodiment of the retainer.

The opaque, metallic, annular portion 185 of the grommet outer end wall184 visually highlights the location of the pre-formed slit 190 andguides insertion of the setscrew hex wrench therethrough.Advantageously, the retainer cap sidewall 254 fitted into thecylindrical retention groove 234, 234′ reinforces the material of theconnector header body 110 that otherwise becomes dimensionally lessstable due to chronic immersion in body fluids and/or pressure appliedby the penetrable grommet 180 against the grommet aperture side wall137. In particular, the ring 236 of the thermoplastic material of theheader body 110 and the grommet aperture sidewall 137 are stabilized bythe rigid metallic retainer cap sidewall 254 fitted into the cylindricalretention groove 234, 234′. The retainer cap sidewall 254 is preferablya continuous sidewall although it can comprise a plurality of spacedapart sidewall segments.

The width of the cylindrical retention groove 234, 234′ and thethickness of the rigid metallic retainer cap sidewall 254 can bespecified to provide an interference fit requiring a specified force toinsert and seat the retainer cap sidewall 254 into the cylindricalretention groove 234, 234′. In some embodiments, at least one retentionelement is provided to enhance the holding force of the retainer capsidewall 254 within the cylindrical retention groove 234, 234′ duringimplantation and over prolonged chronic implantation in body fluids.

For example, the retainer cap 250′ illustrated in FIG. 8 incorporates aplurality of stamped retention flanges 260, 262, 264, 266, 268, etc.,formed through the retainer cap sidewall 254 to extend inward or outwardand distributed around the circumference of the retainer cap sidewall254. The outward extending edges of the retention flanges 260, 262, 264,266, 268, etc., bite into a sidewall of the retention groove 234, 234′and resist dislodgement of the retainer cap 250′. The number and shapeof the retention flanges can be varied from those shown in FIG. 8.

It will also be appreciated that the retention flanges 260, 262, 264,266, 268, etc., can be employed as enhancements for promoting adhesionwith the header body upon application of thermal energy to thethermoplastic material of the header body contacting the enhancements.Ultrasonic welding techniques of the type described in theabove-referenced Publication No. 2003/0040780 can be employed to effectthe thermal welding, particularly where the retention flanges 260, 262,264, 266, 268, etc., bite into a sidewall of the retention groove 234,234′. The ultrasonic energy applied against the outer annular side 252by the shaped head of an ultrasonic generator concentrates where theedges of the retention flanges 260, 262, 264, 266, 268, etc., contactthe thermoplastic material of the header body 110. Localized melting ofthe thermoplastic material occurs along the edges that enhances adhesionof the retention flanges 260, 262, 264, 266, 268, etc., with thesidewall of the retention groove 234 upon cooling.

Further enhancements of the interface between the retention groove 234and the rigid metallic retainer cap sidewall 254 are depicted in FIGS.16–19 that can be employed with or without the depicted retentionflanges 260, 262, 264, 266, 268, etc. In this aspect of the invention,the enhancements comprise at least one aperture through the cap sidewall254 into which thermoplastic material flows upon melting throughapplication of thermal energy and solidifies upon cooling of thethermoplastic material. In one approach to forming such apertures,triangular notches 270, 272, 274, 276, etc., having key slots extendingto the free edge of the cap sidewall 254 are formed in the retainer capsidewall 254 distributed around the circumference thereof. Acorresponding number of keys 284 are formed in the groove 234′ as shownin FIGS. 17 and 18.

During assembly, the cap sidewall 254 is inserted into the groove 234′surrounding the grommet aperture 136 so that each key 284 fits into anotch, e.g., notch 274, as shown in FIG. 17, and points of contact areachieved as shown in FIG. 18. Force and ultrasonic energy are appliedagainst the outer annular side 252 of the retainer cap 250″ as shown inFIG. 18. Each key 284 heats until it melts as it is vibrated by theultrasonic energy transmitted to the points of contact. The melted keymaterial fills the triangular notch 274 and interlocks therewith uponcooling as shown in FIG. 19. It will be understood that the notches 270,272, 274, 276, etc., can take other shapes, e.g., circular rather thantriangular shapes.

All patents and publications referenced herein are hereby incorporatedby reference in their entireties.

It will be understood that certain of the above-described structures,functions and operations of the above-described preferred embodimentsare not necessary to practice the present invention and are included inthe description simply for completeness of an exemplary embodiment orembodiments. It will also be understood that there may be otherstructures, functions and operations ancillary to the typical operationof mechanical instruments that are not disclosed and are not necessaryto the practice of the present invention.

In addition, it will be understood that specifically describedstructures, functions and operations set forth in the above-referencedpatents can be practiced in conjunction with the present invention, butthey are not essential to its practice.

It is therefore to be understood, that within the scope of the appendedclaims, the invention may be practiced otherwise than as specificallydescribed without actually departing from the spirit and scope of thepresent invention.

1. An implantable medical device having a connector header adapted to becoupled through the use of a tool to an electrical lead connectorelement of an elongated electrical medical lead, wherein: the connectorheader is formed of a dielectric header body having at least one headerconnector bore and a header grommet aperture having a grommet aperturesidewall; a connector block is disposed within the connector headerhaving a threaded bore aligned with the header grommet aperture and aconnector block bore aligned with the header connector bore adapted toreceive the lead connector element when a proximal connector assembly ofthe elongated electrical medical lead is received in the headerconnector bore; a setscrew is threaded into the threaded bore having asetscrew socket disposed to be engaged by the tool to enable rotation ofthe setscrew within the threaded bore to tighten the setscrew against orto loosen the setscrew from a lead connector element received in theheader connector bore; and a penetrable grommet is disposed within theheader grommet aperture, the penetrable grommet comprising a generallycylindrical elastomer body having a grommet central axis and including apre-formed resealable slit extending between opposed grommet inner andouter end walls enabling passage of the tool therethrough into thesetscrew socket for rotating the setscrew and sealing of the pre-formedslit upon withdrawal of the tool, the elastomer body comprising acompound of silicone rubber filled with an additive decreasing thetendency of slit healing over time and facilitating passage of the tooltherethrough into the setscrew socket for rotating the setscrew andsealing of the slit upon withdrawal of the tool.
 2. The implantablemedical device of claim 1, wherein the elastomer body of the penetrablegrommet is formed of a compound of silicone rubber compounded withtitanium dioxide in a concentration of up to about two percent byweight.
 3. The implantable medical device of claim 2, wherein: theheader body is formed of a dielectric material of a first color, and theadditive colors the compound in a color contrasting from the first colorproviding a visible target for precisely aligning and inserting the toolthrough the central bore and the slit into operative engagement with thesetscrew.
 4. The implantable medical device of claim 1, wherein: theheader body is formed of a dielectric material of a first color, and theadditive colors the compound in a color contrasting from the first colorproviding a visible target for precisely aligning and inserting the toolthrough the central bore and the pre-formed slit into operativeengagement with the setscrew.
 5. The implantable medical device of claim1, wherein the generally cylindrical elastomer body of the penetrablegrommet includes a grommet sidewall extending between the opposed innerand outer end walls, the grommet sidewall formed having an irregularsurface comprising a plurality of peaks and valleys that maintains fluidsealing contact with the cylindrical sidewall of the tubular headergrommet aperture without adhesive therebetween.
 6. The implantablemedical device of claim 5, wherein the grommet aperture has a nominalinner diameter and the grommet sidewall is formed having a nominalpeak-to-peak outer diameter exceeding the nominal inner diameter of thesidewall to provide a low pressure interference fit upon insertion ofthe penetrable grommet into the header grommet aperture, whereby a low,uniform, interference pressure is attained over a wide tolerance uponassembly that is maintained even if the inner diameter of thecylindrical sidewall of the tubular header grommet aperture changes overextended time periods.
 7. The implantable medical device of claim 5,wherein the grommet aperture has a nominal inner diameter and thegrommet sidewall is formed having a plurality of sealing rings havingnominal sealing ring outer diameters exceeding the nominal innerdiameter of the sidewall to provide a low pressure interference fit uponinsertion of the penetrable grommet into the header grommet aperture,whereby a low, uniform, interference pressure is attained over a widetolerance upon assembly that is maintained even if the inner diameter ofthe cylindrical sidewall of the tubular header grommet aperture changesover extended time periods.
 8. The implantable medical device of claim1, wherein a yield space is provided between the inner end wall of thegrommet and the setscrew socket to accommodate the elastomer body of thegrommet that is pushed inward by the tool advanced through thepre-formed slit.
 9. The implantable medical device of claim 8, whereinthe yield space is provided at least in part by a recess extending intothe inner end wall of the penetrable grommet.
 10. An implantable medicaldevice having a connector header adapted to be coupled through the useof a tool to an electrical lead connector element of an elongatedelectrical medical lead, wherein: the connector header is formed of aheader body formed of a material of a first color and having at leastone header connector bore and a header grommet aperture having a grommetaperture sidewall; a connector block is disposed within the connectorheader having a threaded bore aligned with the header grommet apertureand a connector block bore aligned with the header connector boreadapted to receive the lead connector element when a proximal connectorassembly of the elongated electrical medical lead is received in theheader connector bore; a setscrew is threaded into the threaded borehaving a setscrew socket disposed to be engaged by the tool to enablerotation of the setscrew within the threaded bore to tighten thesetscrew against or to loosen the setscrew from a lead connector elementreceived in the header connector bore; and a penetrable grommet isdisposed within the header grommet aperture, the penetrable grommetcomprising a generally cylindrical elastomer body having a grommetcentral axis and including a resealable pre-formed slit extendingbetween opposed inner and outer end walls enabling passage of the tooltherethrough into the setscrew socket for rotating the setscrew andsealing of the pre-formed slit upon withdrawal of the tool, theelastomer body comprising a compound of silicone rubber filled with anadditive that colors the compound in a color contrasting from the firstcolor providing a visible target for precisely aligning and insertingthe tool through the central bore and the pre-formed slit into operativeengagement with the setscrew.
 11. The implantable medical device ofclaim 10, wherein the penetrable grommet disposed within the headergrommet aperture is formed of a compound of silicone rubber compoundedwith titanium dioxide in a concentration of up to about two percent byweight.
 12. The implantable medical device of claim 10, wherein thegenerally cylindrical elastomer body of the penetrable grommet includesa grommet sidewall extending between the opposed inner and outer endwalls, the grommet sidewall formed having an irregular surfacecomprising a plurality of peaks and valleys that maintains fluid sealingcontact with the cylindrical sidewall of the tubular header grommetaperture without adhesive therebetween.
 13. The implantable medicaldevice of claim 12, wherein the grommet aperture has a nominal innerdiameter and the grommet sidewall is formed having a nominalpeak-to-peak outer diameter exceeding the nominal inner diameter of thesidewall to provide a low pressure interference fit upon insertion ofthe penetrable grommet into the header grommet aperture, whereby a low,uniform, interference pressure is attained over a wide tolerance uponassembly that is maintained even if the inner diameter of thecylindrical sidewall of the tubular header grommet aperture changes overextended time periods.
 14. The implantable medical device of claim 12,wherein the grommet aperture has a nominal inner diameter and thegrommet sidewall is formed having a plurality of sealing rings havingnominal sealing ring outer diameters exceeding the nominal innerdiameter of the sidewall to provide a low pressure interference fit uponinsertion of the penetrable grommet into the header grommet aperture,whereby a low, uniform, interference pressure is attained over a widetolerance upon assembly that is maintained even if the inner diameter ofthe cylindrical sidewall of the tubular header grommet aperture changesover extended time periods.
 15. The implantable medical device of claim10, wherein a yield space is provided between the inner end wall of thegrommet and the setscrew socket to accommodate the elastomer body of thegrommet that is pushed inward by the tool advanced through the slit. 16.The implantable medical device of claim 15, wherein the yield space isprovided at least in part by a recess extending into the inner end wallof the penetrable grommet.
 17. An implantable medical device having aconnector header adapted to be coupled through the use of a tool to anelectrical lead connector element of an elongated electrical medicallead, wherein: the connector header is formed of a dielectric headerbody having at least one header connector bore and a header grommetaperture having a grommet aperture sidewall; a connector block isdisposed within the connector header having a threaded bore aligned withthe header grommet aperture and a connector block bore aligned with theheader connector bore adapted to receive a lead connector element when aproximal connector assembly of the elongated electrical medical lead isreceived in the header connector bore; a setscrew is threaded into thethreaded bore having a setscrew socket disposed to be engaged by thetool to enable rotation of the setscrew within the threaded bore totighten the setscrew against or to loosen the setscrew from a leadconnector element received in the header connector bore; a penetrablegrommet is disposed within the header grommet aperture, the penetrablegrommet comprising a generally cylindrical elastomer body having agrommet central axis and including a resealable pre-formed slitextending between opposed grommet inner and outer end walls enablingpassage of the tool therethrough into the setscrew socket for rotatingthe setscrew and sealing of the pre-formed slit upon withdrawal of thetool; and the generally cylindrical elastomer body of the penetrablegrommet includes a grommet sidewall extending between the opposedgrommet inner and outer end walls, the grommet sidewall formed having anirregular surface comprising a plurality of peaks and valleys thatmaintains fluid sealing contact with the cylindrical sidewall of thetubular header grommet aperture without adhesive therebetween.
 18. Theimplantable medical device of claim 17, wherein the grommet aperture hasa nominal inner diameter and the grommet sidewall is formed having anominal peak-to-peak outer diameter exceeding the nominal inner diameterof the sidewall to provide a low pressure interference fit uponinsertion of the penetrable grommet into the header grommet aperture,whereby a low, uniform, interference pressure is attained over a widetolerance upon assembly that is maintained even if the inner diameter ofthe cylindrical sidewall of the tubular header grommet aperture changesover extended time periods.
 19. The implantable medical device of claim18, wherein a yield space is provided between the inner end wall of thegrommet and the setscrew socket to accommodate the elastomer body of thegrommet that is pushed inward by the tool advanced through thepre-formed slit.
 20. The implantable medical device of claim 19, whereinthe yield space is provided at least in part by a recess extending intothe inner end wall of the penetrable grommet.
 21. The implantablemedical device of claim 17, wherein the grommet aperture has a nominalinner diameter and the grommet sidewall is formed having a plurality ofsealing rings having nominal sealing ring outer diameters exceeding thenominal inner diameter of the sidewall to provide a low pressureinterference fit upon insertion of the penetrable grommet into theheader grommet aperture, whereby a low, uniform, interference pressureis attained over a wide tolerance upon assembly that is maintained evenif the inner diameter of the cylindrical sidewall of the tubular headergrommet aperture changes over extended time periods.
 22. The implantablemedical device of claim 21, wherein a yield space is provided betweenthe inner end wall of the grommet and the setscrew socket to accommodatethe elastomer body of the grommet that is pushed inward by the tooladvanced through the pre-formed slit.
 23. The implantable medical deviceof claim 22, wherein the yield space is provided at least in part by arecess extending into the inner end wall of the penetrable grommet.